The immunomodulatory opioid peptides have been implicated in the neuroimmunopathogenesis of human immunodeficiency virus (HIV)-1 infection and acquired immunodeficiency syndrome (AIDS) dementia However, little is known about the impact of the endogenous opioid peptides (EOP) on the replication of HIV-1 within the brain and on the neurotoxic effect of HIV- 1-related proteins (e.g., gp12O and tat). Our principal hypothesis is that kappa opioid peptides play an immunomodulatory role in the central nervous system via their interaction with specific receptors on glial cells (i.e., microglia and astrocytes), and that this interaction enhances cytokine and nitric oxide (NO) production by these brain immune cells with consequences related to HIV-1 replication and injury in the brain. In vitro cultures of both fetal and adult human microglia and astrocytes will be used to characterize kappa opioid peptide receptors on human brain glial cells (Specific Aim l), to investigate the effect of kappa opioid peptides and of EOP receptor antagonists on HIV-1 replication in human brain cell cultures and purified microglial cell cultures (Specific Aim 2), and to assess the effect of kappa opioid peptides and of EOP receptor antagonists on gp120- and tat-induced neurotoxicity (Specific Aim 3). Glial cells, cytokines, and NO appear to play a central role in the neuropathogenesis of HIV-1 infection and HIV-1-related neurotoxicity. The effect of kappa opioid peptides and EOP receptor antagonists on cytokine production (e.g., tumor necrosis factor-alpha, interleukin [IL]-1, IL-6) by microglial cells and NO production by astrocytes will be explored. Furthermore, we have developed two models of HIV-1 SF162 infection of primary mixed glial/neuronal cell cultures and of enriched microglial cell cultures in order to explore the effect of kappa opioid peptides and of EOP receptor antagonists on HIV-1 replication. Finally, by using human fetal neuronal cell cultures, we will assess the effect of kappa opioid peptides and of EOP receptor antagonists on gpl20- and tat-induced neurotoxicity. These studies of brain immune cells, a target cell population not only for kappa opioid peptides but also for HIV-1 infection, will contribute to our goals of understanding the role of endogenous opioid peptides in the neuroimmunopathogenesis of AIDS in conditions associated with stress including opiate addiction and of devising therapeutic tools that interfere with the development of AIDS dementia.